The present invention pertains to interlocking panels with enhanced ruggedness and improved wind resistance, and in particular, to panels having channel nailing hems primarily intended for use as siding on houses and other structures.
Siding composed of vinyl or other plastic material is a common medium for use as an external covering of a structure. Such siding is fabricated as elongate panels having connectors formed along the lengths of the upper and lower edges. In use, the siding panels are arranged in horizontal interlocking tiers. In general, siding panels include a top lock that is configured to interlock with a bottom lock of another panel. A nailing hem comprising a series of slots for receiving nails to attach the panel to an underlying structure is generally provided near the top lock of each panel.
A premium siding panel will frequently be formed by a pair of materials fused together. The outer layer or capstock is composed of a weather, wear and impact resistant material which also provides a good appearance. The underlayer or substrate is composed of a stiffer material to increase the strength of the panel. A focus of vinyl siding development has been improved resistance to winds. When a building is buffeted by winds, the stress concentration occurs at the nail slots in the nailing hem, and various configurations have been proposed to improve the attachment of the panel to the underlaying wall.
Conventional nailing hems can be classified into three general categories: single thickness, multiple thickness and rollover. Examples of single thickness nailing hems are illustrated in FIGS. 1A-2B. In FIGS. 1A-1B and 2A-2B, conventional siding panel 10 includes a top lock 12, a nailing hem 14, a bottom lock 16, and a medial body 18. Body 18 ordinarily has a pair of faces 20, 22 separated by a center butt 24. Top lock 12 is bent to form a dogleg protrusion 26 which extends downwardly over the upper face 20 of the siding panel to form a groove 28. Bottom lock 16 has a channel-like shape. The distal wall 30 of the bottom lock is inclined back toward the lower face 22 of the body. The distal wall 30 of one panel is snugly fit within groove 28 of another panel to interlock the adjacent siding panels. Nailing hem 14 extends upward from top lock 12 and is provided with elongated slots 32 into which siding nails N or staples or screws are driven to attach the panel to an underlaying wall.
In general siding nails are not driven into the wall fully so that the nail head undersurface does not bear against the nailing hem. This clearance accommodates movement of the panels which occur due to fluctuations in temperature and other environmental conditions. In general, when nails N are driven through the nail slots, and the installed panels are exposed to winds, the panel will tend to move in the direction of arrow A in FIG. 1B. This forces the panel against the nail head and the nail head exerts a load on a flat surface of the panel. The nail slot is thus the locus of a stress concentration, and eventually the slot can open further and ultimately can tear due to wind load.
The panel of FIGS. 1A-1B has a conventional lock geometry, and the panel of FIGS. 2A-2B has a more robust lock geometry in which the top lock occupies much more of the space in the channel-like bottom lock.
Examples of nailing hems configured of a double thickness of siding material are shown in FIGS. 3A-3B and 4A-4B. Double thickness nailing hems are formed by providing additional panel material in a folded-over configuration. Siding panel 10 of FIGS. 3A-3B includes a variation on the top and bottom locks as well. Top lock 12 has an integrally formed double thickness nailing hem 14 above the lock structure, and a triangular cross-section lock with a free leg 34 opposite the upper face 20. Bottom lock 16 has on its distal wall 30 an integrally formed hook 36 at its tip. When adjacent panels are interconnected, hook 36 of the bottom lock slides past free leg 34 of the adjacent lock and fits snugly against upper face 20 as shown in FIG. 3B. Nailing hem 14 is provided with elongated nail slots to receive siding nails N or staples. Another embodiment of a double thickness nailing hem 14 is shown in FIGS. 4A-4B which shows a reinforced dog-leg type top lock 12. The lock structure in this type of panel is configured so that the top lock occupies much of the space in the channel shape of the bottom lock so that the top lock abuts against lower face 22 of the adjacent panel. The top lock is also reinforced with an additional strip of material to enhance the rigidity of the panel, particularly in the lock area. Again, as with single thickness nailing hems, siding nails N are driven only to the extent that the undersurface of the nail head does not contact the nailing hem. While the double thickness nailing hem provides improved strength, the stress concentrations around the nail slot are still present and pose the same problems as the single thickness. That is, when subject to high winds, the nail head will tend to further open the slots and can ultimately lead to failure.
Examples of nailing hems with a rollover shape are shown in FIGS. 5A-5B and 6A-6B. Panel 10 illustrated in FIGS. 5A-5B has a conventional lock structure with nailing hem 14 extending above top lock 12. Nailing hem 14 has an open roll 40 formed at its top end. Siding nails N or staples or screws are driven to secure panel 10 to the extent that the undersurface of the nail head bears against roll 40. The panel illustrated in FIGS. 6A-6B also has a conventional lock structure with nailing hem 14 extending above the top lock. Nailing hem 14 has a closed roll 42 formed at its top end. Siding nails N are driven to secure panel 10 to the extent that the undersurface of the nail head bears against roll 42. In both of these types of nailing hems, elongate slots are provided for siding nails N. In these rollover nailing hems, much of the force that the nails exert on the nailing hems are borne by the roll portions to alleviate the stress concentrations on the nail slots. However, rollover nailing hems are an imperfect solution because upon wind loading, the panels tend to move and the nail head tends to exert a load on the flat surfaces around the nail slots making tearing and failure more likely.
The present invention pertains to interlocking panels having a channel nailing hem above the top lock. A channel nailing hem provides improved nail holding capacity which translates to increased wind resistance, and more rigidity to the panel. The panel has a top lock, a medial body portion, and a bottom lock. The locks are complementary in shape so that they interlock with other panels of like construction.
The rigidity of the panel can be further enhanced by forming the panel with areas of increased substrate thickness along selected portions of the panel. Another way is to affix an additional strip of material to at least one of the lock portions or other panel portion for rigidifying the panel. The strip can be of the same material as the panel or a higher strength material, and can be co-extruded with the panel. Greater rigidity enables easier installation of the panels in an interlocked manner. The panels of the present invention can even be installed by one person. Moreover, the present invention provides a stronger overall construction which permits the use of the panels as siding in coastal areas and other environments which have wind load requirements. In those situations, vinyl siding must exhibit increased nail holding capability.
In one aspect of the invention, the channel in the nailing hem has an open rectangular cross-section above the top lock with elongated slots in the base of the channel. When siding nails, staples or screws are driven into the nail slots, the undersurface of the nail or screw head bears against the surfaces formed by the sides of the channel to eliminate stress concentrations around the slots and improve wind resistance. When staples are used, one leg of the staple is driven into the nail slot and the other leg is driven above the top edge of the panel with the crossbar of the staple overlaying one wall of the channel.
In another aspect of the invention, the channel has an open trapezoidal cross-section with the wider side forming the base with elongated slots provided, and the narrower side forming the opening. When siding nails are driven into the nail slots, the undersurface of the nail head bears against the surfaces formed by the sides of the channel. This eliminates stress concentrations around the slots and the narrower opening ensures that the nail heads will remain above the channel.
In yet another aspect of the invention, the channel of the nailing hem itself is reinforced either by forming the substrate with increased thickness, co-extruding a strip of material or by providing a separate trough that fits within the channel. This reinforcement to the nailing hem channel provides more protection against failure around the nail slots and also rigidifies the panel.
In still another aspect of the invention, the panel is reinforced by increasing the thickness of the substrate or by a strip of additional material co-extruded along its length. This reinforcement can be provided anywhere along the panel, most preferably in one or both of the lock elements.
These and other features and advantages of the invention may be more completely understood from the following detailed description of the preferred embodiment of the invention with reference to the accompanying drawings.